I'm using this mod TSL Loot and Immersion Upgrade which I never used before along with The Restored Content Mod 1.8.2. Captain Riken won't talk about Dhagon Ghent after I eliminated all three captains.

2 The only thing I can think of is the modified dlg or ncs files from Onderon I used, which are stored in the Encounters folder. Try removing the Encounters folder from Override and going back to an earlier save on Onderon, and then go through the glitched area again without that folder. If that solves your issue, be sure to let me know.